The present invention relates generally to the art of producing infrared-reflecting coated glass products, and more particularly to non-iridescent, high transmittance, low emissivity, infrared-reflecting coated glass products.
Transparent infrared-reflecting films such as tin oxide may be deposited on a substrate such as glass by a variety of methods, including the application of thermally decomposable compounds to a heated surface. Useful methods for forming transparent infrared reflecting tin oxide films are taught in U.S. Pat. No. 3,107,177 to Saunders et al, U.S. Pat. No. 3,677,814 to Gillery, and U.S. Pat. No. 4,263,335 to Wagner et al.
Tin oxide films are especially effective infrared reflectors at thicknesses of about 1000 to 8000 Angstroms. However, if the thickness is not sufficiently uniform, the films tend to display a multiplicity of interference color effects commonly referred to as iridescence. Such interference effects render the coated glass aesthetically unacceptable for most architectural applications. Iridescence is not observed in thinner films, however, these films have insufficient infrared reflectance to be practically useful. Likewise, iridescence is not observed in thicker films; however, these films tend to be hazy, have relatively low transmittance, and are difficult to make uniformly. Therefore, various methods to mask interference effects have been developed.
U.S. Pat. No. 3,681,042 to Edwards et al discloses coating a surface of float glass by vaporizing a coating material, entraining the vapor in a stream of hot carrier gas, and directing the gas-borne coating material to the glass surface to be coated, which surface is at a coating-receptive temperature.
U.S. Pat. No. 3,710,074 to Stewart discloses an electrically heated multiple glazed window unit having an electrodconductive coating on an enclosed surface and a selective reflecting film having an absolute infrared reflectance of at least 0.17 to improve the heat insulating character of the unit and reduce the visible iridescence of the conductive film.
U.S. Pat. No. 3,850,679 to Sopko et al discloses depositing a metal oxide coating on a hot glass surface by applying a mixture of carrier air, vaporized solvent and vaporized metal-containing coating reactant to the hot glass surface through a nozzle at a Reynolds number exceeding 2500 with the nozzle-to-glass spacing at least 1.25 times the characteristic dimension of the nozzle.
U.S. Pat. No. 3,852,098 to Bloss et al discloses coating a glass substrate with a metal-containing film by heating the glass and contacting the glass with a gaseous mixture from 50 to 100 percent saturated with the vapor of a reactive metal compound at its temperature immediately before contacting the glass. The gaseous mixture is then heated by the glass to a sufficient temperature to cause the metal compound to react thereby depositing the film.
U.S. Pat. No. 4,206,252 to Gordon describes transparent glass windows having a first coating of infrared reflective material displaying iridescence which is markedly reduced by provision of a layer of continuously varying refractive index between the glass and the coating. The invention also encompasses processes for making such windows.
U.S. Pat. No. 4,294,193 to Gordon describes a vapor coating apparatus for producing the coated glass described above wherein a layer between the glass and the infrared reflective coating has a refractive index which increases continuously from the glass to the coating. The apparatus is described as suitable for use in making coatings of gradually changing compositions from gaseous reactants in general.
U.S. Pat. No. 4,325,988 to Wagner discloses a method and apparatus for producing a film on a substrate surface from a cloud of dust-sized particles of a coating reactant, preferably using a jet mill.
U.S. Pat. No. 4,344,986 to Henery discloses a method for depositing a coating from a powder coating reactant wherein turbulence is created in the carrier gas stream.
U.S. Pat. No. 4,377,613 to Gordon discloses transparent window structures comprising a glass sheet bearing a coating of infrared reflective material wherein the observance of iridescence is reduced by provision of a very thin coating system beneath the infrared reflective coating which reflects and refracts light to interfere with the observation or iridescence.
U.S. Pat. No. 4,401,695 to Sopko discloses a method and apparatus for depositing a coating from a gaseous stream of powder coating reactant, wherein the carrier gas is supplied at a high volume rate and low pressure.
U.S. Pat. No. 4,144,362 to Larkin discloses a method of producing a stannic oxide coating on a heated glass article using finely divided liquid monobutyltin trichloride wherein unpyrolyzed reactant is recovered for subsequent reuse.
U.S. Pat. Nos. 4,187,366; 4,206,252 and 4,308,316 to Gordon disclose transparent glass window structures comprising a glass sheet bearing a first coating of infrared reflective material, wherein the observance of iridescence resulting from the first coating is reduced by a second coating of particular refractive index and thickness providing at least two interfaces forming means to reflect and refract light to interfere with the observance of iridescence.